A System‐Dynamics Framework for Identifying Ecohydrological Thresholds and Environmental Water Requirements in a Data‐Scarce Semi‐Arid Wetland Complex

ABSTRACT Determining environmental water requirements and ecohydrological thresholds is essential for sustaining wetland functionality in semi‐arid regions subject to expanding water withdrawals and climatic variability. This study presents an integrated system‐dynamics framework to identify thresholds and water requirements in the Ramsar‐listed Alagol, Ulmagol and Ajigol (AUA) wetland complex in northeastern Iran. The framework couples daily water balance, wetland morphometry, vegetation dynamics, anthropogenic withdrawals and waterbird habitat responses within a STELLA modelling environment. Long‐term seasonal and temporary inundation boundaries were delineated using a multidecadal satellite observation time series (1986–2025) and field evidence to define functional hydrological thresholds, whereas volume–area–elevation relationships converted simulated storage into habitat availability. The model was calibrated for the primary basin (Alagol Wetland) using daily hydrometric and remote‐sensing observations from 2002 to 2025. Scenario simulations (2026–2040) indicate that anthropogenic withdrawals exert a stronger influence on long‐term ecohydrological conditions than projected precipitation variability. Increased withdrawals substantially reduced seasonal inundation, shortened hydroperiods and accelerated drying, particularly in the shallower, morphologically non‐linear Ajigol and Ulmagol basins. Conversely, reducing withdrawal pressures significantly improved threshold attainment and habitat availability, even under unfavourable climatic projections. The framework quantified critical, optimal and ideal storage states, providing quantitative benchmarks for environmental‐flow planning. This reproducible approach links hydrological management to ecological outcomes, offering a transferable tool to support adaptive water allocation in data‐scarce semi‐arid wetlands globally.